Final answer:
In the Middle Ages, unexplained or abnormal behavior was often attributed to supernatural factors due to the lack of scientific understanding prevalent at the time.
Step-by-step explanation:
During the Middle Ages, bizarre behavior was commonly explained as due to supernatural factors. Explanations for phenomena that could not be understood often invoked the presence of religious, astrological, and supernatural entities or forces. This period lacked a comprehensive germ theory and the understanding of biomedical causes for behavior and diseases which are known today, leading to attributions to mystical causes instead.